A plasma processing is a technique indispensable to the manufacture of semiconductor devices. In recent years, a design rule for semiconductor elements constituting an LSI becomes gradually miniaturized with a view to comply with a demand for high-integration and high-speed LSI, and a semiconductor wafer grows in size. In keeping with this trend, a plasma processing apparatus is required to cope with the miniaturization and the size growth.
In cases of a parallel plate plasma processing apparatus and an inductively-coupled plasma processing apparatus, both of which have been extensively used in the art, plasma damage may occur in a fine-size element due to an increased temperature of electrons. Further, since a plasma density is kept high only in a limited region, it is difficult to uniformly plasma-process a large-size semiconductor wafer at an increased speed.
In view of this, attention has been paid to a RLSA (Radial Line Slot Antenna) type microwave plasma processing apparatus capable of uniformly generating plasma with a high density and at a low electron temperature (see, e.g., Patent Reference 1).
The RLSA type microwave plasma processing apparatus is provided with a planar antenna in an upper portion of a chamber, the planar antenna having a multiple number of slots formed in a specified pattern (a radial line slot antenna). With this type of plasma processing apparatus, microwaves generated in a microwave generator are allowed to pass the slots of the planar antenna and are irradiated into a vacuum chamber through a dielectric microwave transmitting board provided below the planar antenna. A gas introduced into the chamber is converted to plasma by means of a microwave electric field. Processing targets such as a semiconductor wafer and the like are processed by the plasma thus generated.
The RLSA type microwave plasma processing apparatus has an ability to realize a high plasma density over a broad region just below the antenna and therefore is capable of performing a uniform plasma processing within a short period of time. Moreover, this apparatus generates plasma having a low electron temperature, which helps to reduce damage to an element.
In the RTSA type microwave plasma processing apparatus, the distribution and stability of plasma varies with process conditions even when the planar antenna used is one and the same. For the very reason, in order to assure uniformity and stability of the plasma, there is a need to optimize pattern of the slots of the planar antenna and a microwave transmitting board each time the process conditions are changed. This task is extremely onerous.
Patent Reference 1 Japanese Patent Laid-open Application No 2000-294550